In present data systems recorded data is being compressed into smaller areas thereby increasing the need for accuracy in detecting the signal and generating clocking signals. Also in later data codes the signal can run longer without having zero crossing points. This fact makes not only the accurate detection of the zero points a much greater necessity but also allows for more errors in data, in terms of extra zero crossings, in the reading of the data when the detection of the zero crossing points are erroneous due to noise.
In the past there have been attempts to delete noise from data signals by differentiating between noise and data on the basis that the data pulses have a greater amplitude. However the noise pulses frequently can be of an amplitude equal to that of the data making such detection erroneous. In addition the amplitude of the data pulses can vary significantly because of other conditions such as head flying height, the strength of the signal recorded, coding et cetera, such that such a system which normally could detect the zero crossings of the data accurately may frequently detect false data pulses because of the noise in the data signal. Thus the amplitude detection for deleting noise from data or other communications signals is not totally effective.
It is the primary object of this invention to provide an improved circuit for accurately detecting zero crossover points of a data signal by effectively deleting the noise from the signal prior to such detection.